Surface mining



Search Room C?? 1&2372961@ Aug. 16, 1932.

R. H. sHERwoQD ET AL SURFACE MINING Filed July 28, 1950 5 Sheets-SheetAll@ 16, 1932- R. H. sHERwooD ET AL. 1,872,016

SURFACE MINING Filed July 28, 1950 3 Sheets-Sheet 2 Aug. 16, 1932. R.|z. SHERWOOD ET AL 1,872,016

SURFACE MINING Filed July 28, 1950 3 Sheets-Sheet 3 Patented Aug. 16,1932 ROBERT I-I. SHERWOOD, OF INDIANAPOLIS,

PATENT OFFICE AND WILLIAM I-I. STEWART, OF IIINTON,

INDIANA, ASSIGNORS TO ALLENDALE MANUFACTURING COMPANY, INC., OF INDIAN-APOLIS, INDIANA, A CORPORATION OF INDIANA SURFACE MINING Application ledJuly 28,

Our invention relates to surface mining, especially of coal.

The object of the invention is to simplify such surface mining, and tolessen its cost; and particularly to simplify and lessen the cost of theloosening explosions, such as those which loosen the overburden,preparatory to the removal of material by the stripping machinery, andto make such explosions more satisfactory, more reliable, more uniformlydistributed, and more accurately controlled. y

In carrying out our invention, as applied for example in the stripmining of coal, we

use a stripping shovel7 a coal-loading shovel,

and coal-carrying cars in the now well-known way. In order to make iteconomically possible for the stripping shovel to strip the overburden,the latter is loosened by explosions.

Prior to our invention, the explosive for the loosening explosions insurface mining has been put in the bottoms of vertical holes, drilledfrom the natural surface of the ground. This often made it necessary touse the higher types of explosives, both toconcentrate the explosiveforce at the bottoms of the holes and because of diiiculty encounteredwith some explosives from water which seeped into the vertical holes andfilled the bottom parts thereof. The cost of drilling these deepvertical holes has been a very material factor in the cost of surfacemining, especially when the overburden has included hard-rock strata;and if the overburden included easy-fiowng material, such as mud orquick sand, the cost of the vertical holes rose enormously, on accountof the expense necessary for casing them and for loading the explosivewith the casings in place.

In accordance with our invention, we drill long substantially horizontalholes for the loosening` explosive, as into the overburden bank, nearthe base thereof in the strip mining of coal; and thus provide a seriesof long horizontal holes which substantially parallel the coal stratumif coal is being mined, and which may be filled to a large extent withexplosive to form a horizontal grille- Work of explosive which is moreeffective to 1930. Serial No. 471,142.

lift and loosen the overlying material. By having the holes horizontal,the strata of rock and easy-flowing material, and the difficultiesresultant therefrom, may be avoided. Because these holes are horizontal,or may even slope slightly upward, there is little or no tendency forwater to collect in them to any depth. For these reasons, it becomespossible to use a cheaper and less dangerous explosive, such as blackpowder. In addition, by enlarging the inner ends of the horizontalholes, as by small preliminary explosions, and filling with explosiveboth these enlargements and a considerable length of the stems of thehorizontal holes which lead to said enlargements, a horizontalgrillework of explosive, somewhat concentrated at the inner ends of theholes but also underlying -the whole section of material to be loosened,

is obtained; and this greatly increases the effectiveness of theultimate loosening explosion, which is desirably of the explosive in agroup of holes simultaneously, and lessens the amount of explosivenecessary for a given loosening effect. As a result, the cost ofproducing the loosening explosions, which in the strip mining of coalnormally amounts to about twenty-five per cent (25%) of the whole cost,is materially reduced, by from a third to a half. This reduces thetota-l cost of the surface mining; and the resultant cost of the productto the ultimate consumer.

The accompanying drawings illustrate my invention: Fig. l is ageneralized vertical cross-section through a strip mine for coal,including the mechanism for drilling the horizontal holes for theexplosive; Fig. 2 is a fragmentary plan of the strip mine shown in Fig.1, and shows the stripping shovel, the coal-loading shovel, the relationof the strata of coal to the steam shovels and to the overburden and thespoil bank, and the arrangement of long horizontal holes and thedrilling mechanism therefor; Fig. 3 is an enlarged side elevation of thedrilling mechanism for the long explosive-containing holes; Fig. 4. is aplan of the drilling mechanism of Fig. 3; Fig. 5 is a. group offragmentary views showing disassembled a group of parts that go to makeup the drill; Fig. 6 is a front elevai l a 5 (-7 of Fig. 3; Fig. 8 is asection substaiitially on the line 8-8 of Fig. 3; Fig. 9 is a sectionsubstantially on the line 9-9 of Fig. 7; Fig. 10 is a fragmentary viewshowing the chuck for the drill of Fig. 5; and Fig. 11 is 0 an enlaigedfragmentary vertical section through one of the explosive holes,somewhat shortened longitudinally of the hole over the proportions thatwould obtain in actual practice to show the packing of the hole with ex-5 plosive.

We will describe our invention, example, in connection with the ing ofcoal.

The coa-l stratum that is obtained in the by way of strip minstripmining of coal lies beneath a generally horizontal stratified overburden16 which is usually not over fifty (50) feet thick and varies inaccordance with the local geology. The overburden usually includes oneor more strata 16 of generally firm rock, and sometimes strata of sand,mud, and dirt, sometimes witli embedded rocks and boulders 17; and atthe bottom usually has a layer of shale or slate 18, which .isrelatively soft, directly overlying the coal.

The stripping shovel 20, usually mounted on its own caterpillars 21,travels on the stratum of coal 15, in a gully of its own making betweenthe overburden bank on one side 5 and a spoil bank 22 on the other side;and

removes the overburden from one side of such gully and deposits the dirtthus removed upon the spoil bank at the other side thereof as it travelsslowly along such gully. By thus re- 49 moving the overburden, itexposes the stratum 15 of coal. The exposed coal of the coal-stratum 15is removed by a coal-loading shovel 25, also traveling on its owncaterpillars 26; and this coal-loading shovel follows the strippingshovel along the gully and loads the coal into cars 27 which travel on atrack 28 that is laid on the exposed. coal 15 and leads to the usualtipple.

So far this is standard construction in the strip mining of coal.

In order that the stripping shovel 20 may be able to remove theoverburden 16, it is essential, at least from an economical standpoint,that such overburden be first loosened by explosions within it, butpreferably is at least in large part, and desirably substantiallywholly, left in place in the overburden bank so that it will not fiow orfall down into the gully and interfere with operations there. In orderto obtain such loosening, we drill into the overburden bank 16 a seriesof long horizontal holes 30. These long horizontal holes are near thebottom of the overburden, and usually in the stratum of relatively softshale or slate 18 and within from one to three feet of the top of thecoal-stratuin 15. We prefer that they extend lengthwise into theoverburden bank for a distance nearly or quite equal to the height ofthe bank usuall from tei; (1o) to forty (4o) no precise length of holeis essential) and for an overburden of fifty (50) feetdepth We havefound that a spacing of from fifteen (15). to twenty-fw@ (25) feetbetween successive holes gives Satisfactory results. Of C0uIse, thelength o f the holes and the spac ings between holes varies with thenature and height of the overburden.

When the long horizontal holes 30 have been drilled, we have found thatit is desirable to. detonate small explosive charges (springing charges)within them at their 'inner ends, to produce enlargements 31 at suchinner ends, in which the bulk of the final explosive may be placed.

After the enlargements 31 have been made, such enlargements and part ofthe stems of the long horizontal holes 30 which respectively lead tothem are filled with a suitable explosive 32, which may be ordinaryblack powder. (See Fig. 11.) After such filling the outer ends of theholes are plugged, as with clay Before the plugging, and iiideed beforethe filling with powder, a suit* able detonator 34 is put in place inthe hole for detonating the chargeof powder 32 when desired. When asufiicient number of holes 30 have been drilled and charged, the chargesin them may be exploded simultaneously, which effectively produces aloosening and breaking up of the overburden 16 which that series ofholes underlies, but leaves most and usually all of it in substantiallyits original location, without any subsequent washing down into thegully, so that the stripping shovel may then remove that loosenedoverburden from that overburden bank and transfer it to the spoil bank22.

In order to drill the holes 30, we use the drill mechanism shown inFigs. 3 to 10 inclusive. This drill mechanism consists of a frame 40having two parallel rails 41 which form a track upon which a carriage 42may travel toward and from the overburden bank. The frame 40 is putsubstantially perpendicular to the bank, and rests on the exposed coalstratum 15 in line with the hole 30 which it is desired to drill. Thecarriage 42 has wheels or rollers 42 by which it travels on the rails41, and has parts such as fingers 42" Which underlie the heads of therails 41 to prevent the carriage from tilting.

On the carriage 42 is a drill-driving motor 43, usually an electricmotor, which is connected by gears 44 to a drill-shaft 45 also suitablymounted on the carriage in supporting,r trunnions 46 fixed to suchcarriage. Fixed on that end of the drill-shaft 45 opposite the gears 44is a drill-chuck 47, shown as a collar, between which and the trunnion46 is feet, (although Q52, Manno.

stamane a ict HARvEsnNG desirably a thrust bearing 48. The end of thedrill-chuck 47 receives the shank 49 of a drill 50.

This drill is made in sections. There are a plurality of sections 51,each desirably having a rectangular shank 52 projecting from both endsof it; and a plurality of coupling sections 53 having correspondinglyrectangular holes 54 in its ends for receiving the rectangular shanks52. The rectangular shanks 52 correspond in general to the shank 49. Anynumber of sections 51 and 53 may be used to build up a drill-stem of anylength; and this drillstem may be lengthened as the depth of the hole isincreased, by inserting more sections 51 and 53. At the working end ofthe drill there is a drilling section 55, which has a hole 54 which mayreceive one shank 52 of the adjacent drill-section 51. That end of thedrilling section 55 opposite the hole 54 is provided with removable andreplaceable cutting claws 56, which drill the hole 30 somewhat largerthan the outside diameter of the drill-stem, as is clear from Fig. 5.This particular drilling section 55 with its claws 56 is not ourinvention, but is already known, and is called a moles-foot drill. Thevarious sections 51, 53, and 55 of the drill are held together, and thedrill as a whole is held in the drill-chuck 47, by one or more Cotterpins 57 at the various joints. The several sections 51, 53, and 55 areprovided with one or more helical or screw-conveyor iianges 58, forfeeding rearward along the drill and out of the hole 30 the earth andstone which the drilling section 55 has cut loose. These flanges 58 alsoserve to guide the drill. The drill is thus a sectional auger drill.

In the horizontal plane of the drill shaft 45 the carriage 42 isprovided at each side with an eye 60, to which is attached one end of acable 61. Each cable 61 extends forward from its eye 6() to a pulley 62carried in an upright 63 at the forward end of the frame 40, and thencerearward to a winding drum 64. The two winding drums 64 for the twocables 61 are on a cross-shaft 65, which may be manually turned, as by acrank 66. The cross-shaft 65 carries a third winding drum 67, aroundwhich extends a third `cable 68 in the opposite direction from the waythe cables extend around the drums 64. The cable 68 extends from thedrum 67 to the rear of the carriage 42. Thus by turning the crank 66 inopposite directions, the carriage 42 may' be moved either forward orbackward.

Desirably the cross-shaft 65 is provided with a ratchet wheel 69`co-operating with a pawl 70. which permits free turning of thecross-shaft in the direction necessary to feed the carriage 42 forward.The pawl 70 must be thrown out of engagement with the ratchet 67 inorder to move the carriage 42 rearward.

ref,

Because the drill is necessarily so long, it is desirable to provide aguiding and supporting bracket for it at one or more intermediatepoints. For this purpose, we provide a U-shaped bracket 71 mounted on across-bar 72 which is attached at its ends to the two uprights 63 at theforward end 0f the frame 40, as is clear from Fig. 6. A second andsmilar guiding bracket 74 may be provided on a forward extension 75 ofthe frame.

In drilling 4a hole 30, the frame 40 is set in line with the desiredhole, and a suitable number of sections 51 and 53 are attached to the'drill-shaft 45 and have a drilling section 55 at their ends. Theoperator feeds the carriage forward by the crank 66, to force the drill50 against and into the overburden near the bottom thereof; and themotor 43 rotates the drill as the operator thus feeds it forward. Theoperator feels the resistance offered by the shale or slate to theadvance of the drill, and varies his feeding pressure on the crank 66accordingly.

When the carriage 42 is advanced to the end of the frame 40, the drillis stopped, the carriage 42 is withdrawn to the rear end of the frame40, additional sections 51 and 53 are inserted, and the drillingoperation is resumed as before. This is continued until the desireddepth of hole is obtained.

7e claim as our invention:

1. The method of strip-mining coal which is covered by an overburdenbank containing a rock stratum, which consists in drilling into theoverburden bank near the base thereof and below the rock stratum aseries of long substantially horizontal holes substantially parallelingsuch base, putting explosive charges in said holes, firing those chargesto lift the material of the overburden bank to loosen it While leavingit at least largely in place and to fragmentize such rock stratum,removing the loosened and fragmentized material directly from theoverburden bank to a spoil bank, and then removing the coal that isuncovered by the removal of the overburden bank.

2. The method of exposing a coal seam covered by a generallyhorizontally stratified overburden including one or more strata of irmrock, which comprises drilling into the face of the overburden bank aseries of long holes located above and generally parallel to the upperface of the coal seam and below a stratum of firm rock, placingexplosive charges in said holes, firing such charges to lift thematerial in the overburden to loosen it and fragmentize thestratum offirm rock above said holes, and then directly removing the loosened andfragmentized overburden material.

3. The method of loosening material in a generally horizontallystratified bank containing solid rock masses and relatively soft lmaterial, Which comprises drilling into the face of the bank near thebase thereof and in the relatively soft material a series of holesgenerally parallel to the stratification, said holes having a lengthapproximating the height of the bank, placing explosive charges in saidholes, and firing said charges to lift the bank material to loosen it.

4. The method of loosening material in a generally horizontallystratified bank containing solid rock masses and relatively softmaterial, which comprises drilling into the face of the bank near thebase thereof and in the relatively soft material v.a series of holesgenerally parallel to the stratiiication, placing explosive charges insaid holes, and firing said charges to lift the bank material to loosenit.

5. The method of loosening material in a generally horizontallystratified bank Containing a stratum of firm rock, which comprisesplacing a plurality of explosive charges beneath said rock stratum Whileleaving it imperforate, and simultaneously firing said charges to liftthe overburden to loosen it and fragmentize said rock-stratum.

6. The method of loosening material in a generally horizontallystratified bank containing a stratum of firm rock, which comprisesplacing a plurality of explosive charges beneath said rock stratum Whileleaving it imperforate, and tiring said charges to lift the overburdento loosen it and fragmentize said rock-stratum.

7. The method set forth in claim 2 With the addition of a step ofexploding springing charges in said holes before placing the mainexplosive charges therein.

8. The invention set forth in claim 4 With the addition of the step ofexploding springing charges in said holes before placing the mainexplosive charges therein.

9. The method of exposing a coal seam covered by a generallyhorizontally stratified overburden including a stratum of shale or slatelocated closely above the coal seam, which method comprises drilling aseries of holes into said stratum of shale or slate from the face of theoverburden bank, said holes extending generally parallel to the coalseam, placing explosive charges in said holes, firing such charges tolift the material in the overburden bank to loosen it and fragmentizethe stratum of shale or slate, and then directly removing the loosenedand fragmentized overburden material.

In Witness whereof, We have hereunto set our hands at Indianapolis,Indiana, this 19th day of July, A. D. one thousand nine hundred andthirty.

ROBERT I-I. SHERWOOD. WILLIAM H. STEWART.

